JPH0814275B2 - Knock detection device for internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an internal combustion engine knocking detection device, and more particularly, to an improved knocking detection method, which uses a cylinder pressure change waveform to determine a crank cycle of each cycle. The present invention relates to a knocking detection device that calculates heat generation with respect to a corner, takes, for example, a ratio between heat generation due to normal combustion and heat generation due to knocking, and determines the strength of knock by this value.

(Prior Art) Since electronic control technology has been extensively used for controlling vehicles and engines, various approaches to knocking have been made. In addition to methods such as improving gas flow and gas flow and increasing the octane number of fuel,
Depending on the running condition, the addition time is controlled so as to proceed to the limit where slight knocking occurs that is not felt by the human ear, regardless of differences in fuel properties and changes in the octane number required by the engine over time. Knocking control technology, which seeks to improve fuel economy and power performance for each vehicle, is now being used in mass-produced vehicles.

Recently, the knocking control technology has been applied to each cylinder of a six-cylinder engine. Also, in recent on-board knock control by electronic control, knock detection and quantification technology is important.

Knocking detection methods that are considered to be mountable for automobiles are classified according to the physical quantity to be detected, and there are various methods such as in-cylinder pressure, engine vibration, combustion light, knocking sound, and in-cylinder ion current.

Among them, a typical conventional knocking detection device for an internal combustion engine is described in, for example, “Automotive Technology” 1986 Vol.40 NO11. In this device, an in-cylinder pressure sensor is attached to the spark plug, a high-frequency component near the knocking frequency is detected from the combustion chamber pressure change waveform based on the output of the in-cylinder pressure sensor, and its vibration strength is quantified and statistically processed. The knocking level is decided.

(Problems to be Solved by the Invention) However, in such a conventional knocking detection device for an internal combustion engine, the vibration detected by the in-cylinder pressure sensor is affected by the mounting position, sensor type, sensor type, and detection cylinder. However, it is necessary to adapt the knock detection logic for each engine model, which causes an increase in man-hours and cost, and there is a problem that the detection accuracy is deteriorated when the logic is not sufficiently adapted.

In addition, the in-cylinder pressure sensor used in the conventional knocking detection method is highly effective in that it does not require special processing for the engine, but in addition to combustion pressure, mechanical vibration due to engine vibration and rotation , It is difficult to separate the vibration component that becomes noise with the method that uses the high-frequency signal component obtained from the sensor output, and therefore the regular knock component cannot be accurately detected, and the detection accuracy is sufficient. There was a problem that it was not.

For example, at high rotations, high frequency vibration components increase,
In particular, it becomes difficult to separate the regular knock component.

(Object of the invention) Therefore, the present invention calculates heat generation for a crank angle for each cycle from a pressure change waveform obtained by cutting a high frequency component of the combustion chamber pressure detected by a sensor, for example, heat generation due to normal combustion and heat due to knocking. By taking the generation ratio and determining the knock intensity based on this value, the number of man-hours and costs can be reduced without changing the logic regardless of the engine model and the individual difference in the sensor output, and the detection accuracy can be improved. The purpose is to improve.

(Means for Solving the Problems) In order to achieve the above object, a knocking detection device for an internal combustion engine according to the present invention has a basic conceptual diagram as shown in FIG.
Pressure detection means a for outputting a combustion pressure or a signal that changes in proportion thereto, removal means b for removing a predetermined high frequency component from the output of the pressure detection means a, and operation state detection means for detecting the operation state of the engine c, the crank angle detecting means d for detecting the crank angle of the engine, the pressure change waveform obtained by removing the high frequency component of the combustion pressure detected by the pressure detecting means a, and the operating state of the engine with respect to the crank angle during one cycle. Total heat calculation means e for calculating total heat generation, start point specifying means f for specifying a start point of heat generation due to knocking during one cycle, and knock heat calculation means g for calculating heat generation due to knocking during one cycle And a ratio of one or more of heat generation due to normal combustion or total heat generation in one cycle and heat generation due to knocking is calculated, And a, a knock intensity determining unit h determining knock intensity based on the ratio of.

(Operation) In the present invention, the heat generation for the crank angle of one cycle is calculated from the pressure change waveform obtained by cutting the high frequency component of the combustion chamber pressure detected by the pressure detection means, and then the heat generation (or total heat generation) by normal combustion is calculated. However, the knock intensity is determined based on this ratio.

Therefore, unlike the conventional method of digitizing the vibration intensity, since it is based on the change in heat generation with respect to the crank angle, regardless of the engine model and individual differences in sensor output,
Moreover, it becomes possible to detect knocking accurately without changing the logic.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

2 to 9 are diagrams showing a first embodiment of a knocking detection device for an internal combustion engine according to the present invention, which is an example in which the present invention is applied to a combustion control device.

First, the configuration will be described. FIG. 2 is an overall configuration diagram of the combustion control device. In this figure, 1 is an engine,
Intake air is supplied from an air cleaner 2 to each cylinder through an intake pipe 3, and fuel is injected based on an injection signal Si into an injector 4
Is injected by. The air-fuel mixture in the cylinder explodes and burns due to the discharging action of the ignition plug 5 based on the ignition signal Sp, becomes exhaust gas, and is exhausted from the exhaust pipe 6.

The air flow rate Qa taken into the engine 1 is detected by the air flow meter 7 and controlled by the throttle valve 8 in the intake pipe 3. The intake negative pressure (boost) in the intake pipe 3 is detected by an intake pressure sensor 9, and the crank angle of the engine 1 is detected by a crank angle sensor (crank angle detecting means) 10. The engine speed N is calculated by counting the output pulses of the crank angle sensor 10.

The oxygen concentration in the exhaust gas is detected by the oxygen sensor 11 provided in the exhaust pipe 6, and the temperature of the cooling water flowing through the water jacket is detected by the water temperature sensor 12. Further, the combustion pressure (in-cylinder pressure) of each cylinder is detected by an in-cylinder pressure sensor (pressure detection means) 13, and the in-cylinder pressure sensor 13 is tightened and fixed as a washer of the ignition plug 5. Note that the pressure sensor 13 is not limited to the cylinder pressure sensor 13 as long as it generates a signal that changes in proportion to the combustion pressure. For example, a pressure sensitive element may be incorporated in the body of the ignition plug 5.

The air flow meter 7, the intake pressure sensor 9, the crank angle sensor 10, the oxygen sensor 11 and the water temperature sensor 12 constitute an operating state detecting means 14, and outputs from the operating state detecting means 14 and the in-cylinder pressure sensor 13 are control units. 20
Is input to The control unit 20 is composed of a microcomputer and an electronic circuit, calculates a processing value required for knocking detection and knock suppression control and other combustion control based on the detection effect, and outputs the injection signal Si and the ignition signal Sp. .

Here, among the functions of the control unit 20, the configuration of the part particularly related to knocking detection is shown in FIG. In FIG. 3, the output signal of the in-cylinder pressure sensor 13 is input to the high frequency cut filter 21 to remove a predetermined high frequency component, and then A / D converted by the A / D converter 22.
It is input to the knock intensity calculation circuit 23. The high frequency component is cut in order to effectively remove the noise component when knocking is detected, and the cutoff frequency for cutting the high frequency component is changed in proportion to the engine speed N as shown in FIG. ing. Specifically, the engine speed N is calculated based on the output of the crank angle sensor 10 among the outputs of the operating state detecting means 14, and the filter selection circuit 24 determines the optimum value from the characteristics shown in FIG. 4 based on the calculation result. A cutoff frequency is selected and the fact is output to the high frequency cut filter 21, and the high frequency cut filter 21 cuts off the high frequency component of the selected frequency band.

As the high frequency cut filter 21, for example, an analog filter is used. This filter is a combination of elements in which the resistance component has frequency dependency, and allows the attenuation ratio of the input signal to have frequency dependency, so that it passes or blocks an arbitrary frequency range. There are Bessel filters and Butterworth filters. The high frequency cut filter 21 and the filter selection circuit 24 constitute a removing means 25.

A signal from the operating state detecting means 14 is also input to the knock strength calculating circuit 23, and the knock strength calculating circuit 23 includes a heat generation calculating portion (corresponding to total heat calculating means) 26 and a knocking heat generation start point detecting portion (start). 27, which corresponds to a point specifying means), a knock portion heat generation calculation portion (corresponding to knock heat calculation means) 28, and a knock strength calculation portion (corresponding to knock strength determination means) 29. The heat generation calculation unit 26 calculates the total heat generation for the crank angle during one cycle based on the operating state of the engine 1 from the pressure change waveform obtained by removing the high frequency component of the combustion pressure detected by the in-cylinder pressure sensor 13, and generates the knocking heat. Start point detector
27 specifies the starting point of heat generation due to knocking during one cycle. Further, the knock part heat generation calculation unit 28 calculates the heat generation due to knocking in one cycle, and the knock strength calculation unit 29 calculates the ratio between the total heat generation during the cycle and the heat generation due to knocking, and based on this ratio. The strength of knocking is determined by outputting the determination result to the knocking intensity signal output circuit 30. Knocking strength signal output circuit
Reference numeral 30 denotes an ignition timing control circuit (not shown) in the control unit 20 for generating a knock intensity signal corresponding to the determination result.
And is used for information of knock suppression control. Also,
Not only for knocking control, but it may be used as input data to a knock intensity input meter as data for detecting knock, for example.

 Next, the operation will be described.

When the engine 1 starts operating, the combustion pressure in the combustion chamber of each cylinder changes, and a peak of the combustion pressure appears every cycle. As shown in FIG. 5, the calculation of heat generation in this case is such that the value of the combustion pressure signal from which the high frequency component has been removed is a function of the fuel basic injection amount Tp or the intake negative pressure (boost) or the intake air amount in the knock detection state. It starts from the point where it exceeds the calculated value Po Po = func (Tp or Boost).

The calculation of the heat generation amount is specifically performed as follows. As shown in FIG. 6, assuming that the stroke volume of the cylinder 31 is VST, the fuel chamber volume is VC, the connecting rod length is CL, and the radius is r, the compression ratio rc is And the total volume V (θ) at a certain crank angle θ as shown in FIG. It is expressed by Further, as shown in FIG. 7, from the combustion pressure waveform during the compression stroke, the polytropic index PN is calculated from the combustion pressures P ₁ and P ₂ corresponding to 60 ° and 44 ° before TDC and the volumes V ₁ and V _{2 at} that point. Is calculated as Further, in actuality, the combustion pressure P (I) and the volume V (I) for each unit crank angle are sequentially calculated to obtain the total heat generation amount, but the calculation for each unit crank angle is performed by, for example, FIG. P (I), V as shown in a)
In contrast to (I), P (I + 1), V at the next crank angle
It is calculated as (I + 1), and the breakdown of such a pressure change is as shown in FIG. 8 (b): at timing t ₁ (corresponding to I) and timing t ₂ (corresponding to I + 1), the pressure increase due to combustion increases. And both the pressure increase due to piston movement is included. And one coefficient required for calculation of heat generation
F _K However, if Cv: constant volume specific heat R: gas constant and the stroke volume at the compression start point is V (I) = VST, the total heat generation Q _A It is calculated by

Next, calculate the heat generation part by knocking,
The heat generation portion due to knocking is a portion shown by hatching in FIG. In this case, the inflection point of the heat generation change with respect to the crank angle as the starting point of the heat generation part due to knocking is the midpoint between the heat generation start point and the end point, or the inflection point delayed from the compression top dead center (or ignition timing). Is used as the starting point of heat generation by knocking. By determining the knock start point by such a method, the start point can be specified with high accuracy in accordance with the actual combustion state. On the other hand, as the end point of heat generation due to knocking, a point at which heat generation with respect to the crank angle becomes 0 is used. Then, the amount of heat generated by knocking Q _B
Is obtained by connecting the knock start point and the end point with a straight line and obtaining the heat generation portion (hatching portion) that exceeds this straight line.

When the heat generation amounts Q _A and Q _B are calculated in this manner, the knock strength calculation unit 29 then calculates the ratio S between the total heat generation Q _A and the heat generation Q _B due to knocking. The knock strength is determined based on this ratio S. Therefore, unlike the conventional method in which the vibration intensity is digitized to detect knocking, it is based solely on the change in heat generation with respect to the crank angle.Therefore, the engine model, the mounting position of the cylinder pressure sensor 13, the sensor output, etc. It is possible to detect knocking with high accuracy regardless of individual differences among the above and without requiring a change in the detection logic.

Further, since the vibration component is not the detection target, it is not affected by the noise component based on the vibration, and the knocking detection accuracy can be significantly improved as compared with the conventional case.
In particular, even if the high-frequency vibration component increases in the high rotation range, the regular knock component can be separated by the heat generation analysis, and the detection accuracy improves. As a result, it is possible to reduce the number of man-hours and the cost for developing the knocking detection logic.

In the above embodiment, the ratio S is calculated using the total heat generation Q _A as the denominator, but the present invention is not limited to this. For example, heat generation due to normal combustion (Q _A −Q _B ) is calculated and this is calculated. As a denominator The ratio S may be obtained from the following equation.

Next, FIG. 10 is a view showing a second embodiment of the present invention,
In this embodiment, the structure of the removing means 35 is different from that of the first embodiment. That is, the removing means 35 is a high frequency cut filter.
The high frequency cut filter 36 is composed of a Fourier transform circuit 36a and an inverse Fourier transform circuit 36b.
The / D converter 22 is arranged. Then, the high frequency cut filter 36 expands the input signal A / D converted by the A / D converter 22 into a Fourier series that is a polynomial in which each term corresponds to each frequency, and the frequency range to be cut off in this term A polynomial in which the term corresponding to is deleted is calculated, and the signal is reconstructed from this equation to transmit or cut off an arbitrary frequency range. With such a configuration, the same effect as that of the first embodiment can be obtained.

Next, FIGS. 11 to 14 are views showing a third embodiment of the present invention, and this embodiment is characterized by a knock start point detecting method.
FIG. 11 is a block diagram of the main part, showing only the parts different from the first embodiment. In FIG. 11, the output of the in-cylinder pressure sensor 13 is branched in the middle and is also input to the high-pass filter 41. The high-pass filter 41 allows only a predetermined high-frequency component of the pressure vibration signal to pass and the comparator 42.
Output to. A predetermined reference value is input to the other input terminal of the comparator 42, and the comparator 42 gates a signal of "H" level when the high frequency component of the pressure vibration signal, that is, the predetermined high frequency vibration exceeds the reference value. Output to 43. When the output of the comparator 42 is at the “H” level, the gate 43 reads the crank angle detected by the crank angle sensor 10 and outputs a synchronization signal to the knock intensity calculation circuit 44, which serves as a determination for setting the knock detection flag FKN. The knock strength calculation circuit 44 outputs
In response to the synchronization signal, the process related to the knock detection flag FKN is performed in addition to the process similar to that of the first embodiment. The comparator 42 and the gate 43 constitute a start timing setting means 45. In the present embodiment, the high-pass filter 41, the start timing setting means 45, and the knocking heat generation start point detection section 27 in the knock intensity calculation circuit 23 cooperate with each other to form the start point specifying means 46. Others are the same as the first embodiment.

 Next, the operation will be described.

FIG. 12 is a flowchart that is executed in synchronization with the timing when the output of the gate 43 becomes the “H” level, which is a processing program for the knock detection flag FKN.

First, in step S ₁ , read the crank angle θ this time,
In step S ₂ , the crank angle θ is compared with the predetermined value θ ₃ . θ
₃ is set near TDC, for example. If θ ≧ θ ₃ , then in step S ₃ , the crank angle θ is compared with a predetermined value θ ₄ . θ ₄ is set to 50 ° ATDC, for example. By setting θ ₃ and θ ₄ in this way, as shown in FIG. 13, particularly the high frequency vibration waveform of the vibration component of the in-cylinder pressure sensor 13 substantially coincides with the starting crank angle of knocking, and the level thereof changes abruptly. It has been confirmed by experiments and the like by the present inventor, and according to such a fact, knocking easily occurs between TDC and ATDC 50 °. Therefore, the gate
In synchronization with the output signal of 43, and the crank angle θ is θ ₃ to θ ₄
Determining that knocking has occurred if during the knock detection flag FKN in Step S ₅ is set to "1", the knock detection flag FKN in Step S ₄ deviates from theta ₃ through? ₄ in the section "0" Reset and end the routine.

FIG. 14 is a flow chart showing a program for knock strength determination, and this program is executed in synchronization with a unit crank angle (for example, 1 ° C. A).

First, in step S ₁₁ , the crank angle θ is read, and in step S ₁₂ , the current crank angle θ is compared with the predetermined value θ ₁ . θ ₁ is set to the crank angle of the ignition timing as shown in FIG. 13, for example. If θ ≧ θ ₁ , then in step S ₁₃ , the crank angle θ is compared with a predetermined value θ ₂ .
θ ₂ is set to the expansion bottom dead center BDC as shown in FIG. 13, for example. This is to match the situation that the crank angle for passing the high-pass filter 41 to specify the knock start point is limited to between the ignition crank angle and BDC. Therefore, the crank angle θ this time is θ
₁ through? Knock detection flag in step S ₁₄ if between ₂ F
It is determined whether or not KN is standing, and if it is not between θ ₁ and θ ₂ , this routine is ended. FKN = 1 in step S ₁₄
Determines that there is a heat generation corresponding thereto knocking occurs, the knocking part of the heat generated in the step S ₁₅ when the (13
(Hatched portion in the figure) Q _B is calculated, while when FKN = 0, heat generation Q _C of the non-knock portion is calculated in step S ₁₆ .
Note that Q _C is the total heat generation Q _A minus the knock part total heat generation Q _B. Then, the ratio of the two S for knock intensity calculated in step S ₁₇ As determined by measuring the knock level from the ratio S at step S _18, and ends the routine outputs a knock intensity signal corresponding thereto.

Therefore, in the present embodiment, a predetermined high frequency component is extracted from the combustion chamber pressure oscillation waveform, and the knock start is specified from the oscillation waveform as the knocking start crank angle, which is the crank angle at which the high frequency oscillation starts. compared to can be calculated more accurately knock part heat generation Q _B, there are cormorants effect the accuracy of knocking detection is further improved.

Next, FIGS. 15 to 17 are diagrams showing a fourth embodiment of the present invention, and this embodiment is characterized by the method of calculating the polytropic index.

FIG. 15 is a block diagram of the main part, showing only the parts different from the first embodiment. In Figure 15, A / D
The output of the converter 22 is input to the polytrope exponent calculation circuit 51, which is the crank angle sensor.
Based on the output of 10, the polytropic index is calculated for each cycle from the in-cylinder pressure waveform during the compression stroke, and the calculated value is output to the knock strength calculation circuit 52. In addition to the same processing as that in the first embodiment, the knock strength calculation circuit 52 uses the calculation result of the polytrope index calculation circuit 51, particularly for the polytropic index, to calculate heat generation. In this embodiment, the heat generation calculation section 26 in the polytropic index calculation circuit 51 and the knock strength calculation circuit 52 cooperates to form the total heat calculation means 53. Others are the same as the first embodiment.

First, the background of the present embodiment will be explained. In the first embodiment, the polytropic exponent is actually calculated by several tens.
The combustion pressure of 0 cycles is detected, and it is averaged to calculate the polytropic index, and the calculation of heat generation is performed with the advantage that a smooth diagram can be drawn. However, according to this method, since the polytropic index is calculated at the predetermined crank angle, the combustion pressure of the predetermined crank is affected by, for example, a slight noise or fluctuation of the cylinder pressure signal, so that the calculated value may vary. Therefore, the accuracy of knocking detection may be reduced.

Therefore, in this embodiment, the polytropic index is calculated for each cycle, and the average value thereof is obtained from the in-cylinder pressure detection values before and after the predetermined crank angle, whereby the calculation accuracy of the polytropic index is increased, and as a result, the heat generation is calculated. Is accurate.

FIG. 16 is a flow chart showing a knock intensity determination program. This program is started and executed with reference to a predetermined crank angle, for example, the crank angle at the time when one combustion cycle is completed.

First, the average value of the in-cylinder pressure P ₁ in the first predetermined crank angle at step S ₂₁ Is calculated according to the following equation.

However, 1-N to 1 + N: the crank angle during the compression stroke, and then the average value of the in-cylinder pressure P ₂ at the second predetermined crank angle in step S ₂₂ . Is similarly calculated according to the following equation.

However, 2-N~2 + N: relationship between each crank angle and cylinder pressure waveform at the crank angle step S _21, S ₂₂ during the compression stroke is shown as FIG. 17, the figure larger main portion It was done. Then calculates the polytropic exponent PN according to the following equation at step S _23.

Then, calculates the heat generation of the 1 cycle in the same arithmetic expression in the first embodiment using the polytropic exponent calculated from the above equation in step S _24, to calculate the knock intensity in step S _25, further step S _{At 26} , a knock intensity signal representing the knock level is output and the routine ends.

Therefore, in the present embodiment, since the average value is calculated from the in-cylinder pressure detection values before and after the first and second predetermined crank angles and the polytropic index is calculated for each cycle, noise and fluctuations in the in-cylinder pressure signal. The accuracy of heat generation can be improved regardless of the influence of the above, and the accuracy of knocking detection can be further improved.

Next, FIGS. 18 and 19 are diagrams showing a fifth embodiment of the present invention, in which the learning value is used for the calculation of the polytropic index. FIG. 18 is a block diagram of the main part, showing only the parts different from the first embodiment. In FIG. 18, a part of the output of the operating state detecting means 14 is input to the polytrope exponent calculation circuit 61, and the polytrope exponent calculation circuit 61 is based on the engine load (intake air amount or boost) and the engine speed. The exponent is calculated and the result is output to the polytropic exponent learning circuit 62, and the polytropic exponent learning circuit 62 learns and stores the polytropic exponent.

In addition to the same processing as that in the first embodiment, the knock strength calculation circuit 63 adopts the learning value of the polytrope index learning circuit 62, particularly for the polytropic index, to calculate the heat generation.
In this embodiment, the heat generation calculation block 26 in the polytropic exponent calculation circuit 61, the polytropic exponent learning circuit 62 and the knock strength calculation circuit 63 cooperates to form the total heat calculation means 64. Others are the same as the first embodiment.

FIG. 19 is a flowchart showing a knock determination program. First, the polytropic exponent PNN for each first time in step S ₃₁ (each cycle) for calculating according to the following equation.

Next, in step S ₃₂ , the reference value PN ₀ of the polytropic index corresponding to the current operating region is looked up from the table map divided for each operating region using the engine load and the engine speed as parameters. The reference value PN ₀ is an optimum value stored in advance through experiments or the like. Like in step S ₃₃ is looked up from a table map the learning correction value ΔPNL to the speed and engine load as parameters. This learning correction value ΔPNL is for correcting the reference value PN _{0 according} to the driving conditions and environmental conditions at that time. Then calculates the learning polytropic exponent PN1 in step S ₃₄ in accordance with the following equation.

PN1 = PN ₀ + ΔPNL then calculates the current polytropic exponent PN according to the following equation at step S _35.

However, a: reflection ratio (0 <a <n) n: constant The polytropic index PN is obtained from the actual detection value PNN and the learning value PN1 by this calculation, but regardless of changes in environmental conditions due to learning. The polytropic exponent can be calculated smoothly, and its accuracy becomes extremely high. Next, in step S ₃₆ , the learning correction store value ΔPNLL is calculated from the equation ΔPNLL = PN−PN1 according to the following formula, and this calculated value is stored in the ΔPNL learning table as a learning result in step S ₃₇ . Next, in step S ₃₈ , the current polytropic index P obtained by the above equation is calculated.
Using N, the heat generation during one cycle is calculated by the same calculation formula as in the first embodiment, and the knock intensity is calculated in step S ₃₉ ,
Further to end the routine outputs a knock intensity signal representative of the knock level in step S _40.

Therefore, since the learning value is used for the calculation of the polytropic index PN in the present embodiment, various effects by so-called learning, for example, the reliability of the calculated value, the high accuracy, the high speed of the calculation, etc. can be obtained. The knocking detection accuracy can be further enhanced.

(Effect) According to the present invention, the engine model, the mounting position of the sensor,
It is possible to detect knocking with high accuracy regardless of individual differences in sensor output and without changing the detection logic, and it is possible to reduce the number of knocking detection steps and cost.

[Brief description of drawings]

FIG. 1 is a basic conceptual diagram of the present invention, FIGS. 2 to 9 are diagrams showing a first embodiment of a knocking detection device for an internal combustion engine according to the present invention, FIG. 2 is an overall configuration diagram thereof, and FIG. Is a block configuration diagram of its main part, FIG. 4 is a diagram showing characteristics of its cutoff frequency, FIG. 5 is a diagram explaining a starting point of its heat generation calculation, and FIG. 6 is a diagram showing calculation of its compression ratio. FIG. 7 is a diagram showing a part of the combustion pressure waveform, FIG. 8 (a)
(B) is a diagram for explaining the increase of the combustion pressure, FIG. 9 is a diagram for explaining the calculation of the heat generation, and FIG. 10 is a diagram showing a second embodiment of the knocking detection device for an internal combustion engine according to the present invention. 11 is a block diagram of a portion of the internal combustion engine, and FIG. 11 to FIG. 14 are diagrams showing a third embodiment of a knocking detection device for an internal combustion engine according to the present invention.
FIG. 11 is a block configuration diagram of its main part, and FIG. 12 is a flowchart showing a processing program for the knock detection flag,
FIG. 13 is a waveform diagram for explaining the knock starting point, FIG. 14 is a flow chart showing a program for determining the knock strength, and FIGS. 15 to 17 are the fourth embodiment of the knocking detection device for an internal combustion engine according to the present invention. FIG. 15 is a block diagram showing the main part of the same, FIG. 16 is a flow chart showing a program for determining the knock strength, and FIG. 17 is a diagram showing the relationship between the crank angle and the calculated value of the in-cylinder pressure waveform. Figure, No. 18,
FIG. 19 is a diagram showing a fifth embodiment of the knocking detection device for an internal combustion engine according to the present invention, FIG. 18 is a block configuration diagram of a main part thereof, and FIG. 19 is a flow chart showing a program for knocking strength determination thereof. is there. 1 ... Engine, 4 ... Injector, 5 ... Spark plug, 7 ... Air flow meter, 9 ... Intake pressure sensor, 10 ... Crank angle sensor, 13 ... Cylinder pressure sensor (pressure detection means), 14 ... … Operating condition detection means, 20 …… Control unit, 21, 36 …… High frequency cut filter, 22 …… A / D converter, 23 …… Knock strength calculation circuit, 24 …… Filter selection circuit, 25, 35 …… Removing means, 26 ... Heat generation calculation section (total heat calculation section), 27 ... Knocking heat generation start point detection section (starting point specifying section), 28 ... Knock section heat generation calculation section (knock heat calculation section), 29 …… Knock strength calculation unit (knock strength determination means), 30 …… Knock strength signal output circuit, 41 …… High-pass filter, 42 …… Comparator, 43 …… Gate, 44,52,63 …… Knock strength calculation Circuit, 45 …… Start timing setting means, 46 …… Open Point specifying means 51, 61 ...... polytropic exponent operation circuit, 53, 64 ...... total heat calculating means, 62 ...... polytropic exponent learning circuit.

Claims (1)

[Claims] 1. A) pressure detection means for outputting a combustion pressure or a signal that changes in proportion thereto, b) removal means for removing a predetermined high frequency component from the output of the pressure detection means, and c) operation of the engine. Operating condition detecting means for detecting the state, d) crank angle detecting means for detecting the crank angle of the engine, and e) pressure change waveform and engine operating condition in which the high frequency component of the combustion pressure detected by the pressure detecting means is removed. Total heat calculation means for calculating total heat generation for a crank angle in one cycle based on the following: f) start point specifying means for specifying a start point of heat generation due to knocking in one cycle; g) knocking in one cycle Knock heat calculation means for calculating heat generation by h), and h) one or more of heat generation or total heat generation by normal combustion in one cycle and knockin A knocking detection device for an internal combustion engine, comprising: knocking strength determination means for calculating a ratio to heat generation due to the engine and determining knocking strength based on this ratio.